Friction and Wear Behavior of Micro Arc Oxidation Coatings on Magnesium Alloy at High Temperature

A ceramic coating was formed on AZ91D magnesium alloy by micro arc oxidation technology in aqueous solution containing silicate and phosphate. The phase composition, surface, cross-sectional and wear tracks morphologies of the coating were analyzed by XRD, SEM and Laser Scanning Confocal Microscope (LSCM), respectively. UMT-3 High Temperature Tribometer was used to study the friction and wear behaviors of coating within 150 °C. The results show that the coatings' mean friction coefficient firstly increases with the temperature increasing. When the ambient temperature exceeds 100 °C, it begins to reduce. The wear rate of the coating is much lower than that of magnesium alloy substrate, and it declines as temperature goes up. The results indicate that the micro arc oxidation coating has excellent wear resistance particularly at high temperature. Through the analysis of grinding cracks' micro-structure at the load of 2 N, the main wear mechanism of these coatings at different temperatures is all abrasive wear.